Control of breathing in young twins

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Abstract
To clarify the role of genetics in determining chemical and behavioral control of breathing, an age-, body size-, and sex ratio-matched study was conducted in 62 twins (mean age 16.4 yr, 20 pairs of monozygotic twins (MZ) and 11 pairs of dizygotic twins (DZ)] for ventilatory responses to hypoxia (A) and hypercapnia (S) along with thresholds for perception of added inspiratory resistance. A and S were determined by a dual-control system developed to regulate arterial blood gases at predetermined levels. Mean values for A, S, thresholds for added resistance, and mouth pressure at the threshold were not different between MZ and DZ. Within-pair variances for A, S, and mouth pressure at the threshold were significantly smaller in MZ than DZ. Neither A nor S correlated with thresholds for resistance and mouth pressure in either MZ or DZ. These results indicate that in adolescent twins sensitivity to added inspiratory resistance and chemosensitivity to hypoxia and hypercapnia involve genetically determined factors, and perception of added inspiratory resistance is not directly related to chemical control of breathing.